Heathrow Airport

London Heathrow Airport is the busiest airport in the United
Kingdom, and the third busiest airport in the world. Formed of two
runways and four currently operational terminals - Terminal two is
currently under extensive reconstruction - the airport started as a
small airfield in 1929, with development as a military airfield
beginning in 1944. The Second World War ended before that work
could be completed though, and the government took the decision to
develop the aerodrome into a civilian airport. The first terminal
building, since demolished, was completed in 1955. Heathrow
currently operates at 98% of its total capacity, and is the subject
of ongoing discussion to construct additional runway space.

As a result, filming drama at Heathrow is difficult. The BBC
often uses the British Airways Maintenance Facility at Cardiff
International Airport instead, a three section hanger capable of
heavy maintenance on 747 aircraft. As well as appearing in A
Scandal in Belgravia, the same facility represented Heathrow
onscreen in Torchwood: Miracle Day.